A conventional color printer as an image forming device includes a holder that integrally holds a plurality of photosensitive drums, and an exposure unit that exposes the photosensitive drums to light. More specifically, the exposure unit is supported a metal plate frame constituting a main frame, and the position of the exposure unit is fixed relative to the main frame. The holder is positioned below the exposure unit, and front and rear end portions of the holder are supported to the metal plate frame, so that the position of the holder is fixed relative to the main frame. The exposure unit and the holder are subjected to positioning by the metal plate frame thereby providing an accurate positional relationship between the exposure unit and the holder.